Human cognition can be conceptualized as an axis whereby males tend toward relative strengths in mechanistic ('things' thinking) cognition and females tend toward relative strengths in mentalistic ('people'-thinking) cognition. Psychiatric conditions are hypothesized to reflect the extreme ends of this axis, with over-developed social cognition underlying the psychotic-affective spectrum in contrast to under-developed social cognition characterizing the autism spectrum. Consistent with this hypothesis, I found a diametric relationship between autistic and schizotypal features based on questionnaire data drawn from a large non-clinical sample of undergraduates. I also conducted two literature reviews asking: 1) Is mentalistic cognition enhanced in borderline personality disorder (BPD)? and 2) are BPD and depression associated with extreme female phenotypes? Both conditions involved elevated mentalistic cognition, a female-bias in their prevalence, and associations with female-typical hormonal profiles. These findings provide evidence that psychological variation is organized along an axis shaped by sex differences and that extreme expressions of evolved cognitive systems mediate a suite of psychiatric conditions.
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Thesis advisor: Crespi, Bernard
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